Vascular movement of beet necrotic yellow vein virus in Beta macrocarpa is probably dependent on an RNA 3 sequence domain rather than a gene product.
RNAs 1 and 2 of beet necrotic yellow vein virus (BNYVV) carry the functions enabling viral RNA replication, cell-to-cell movement, virus assembly and vascular movement of the virus in the systemic host Spinacea oleracea. In Beta macrocarpa, on the other hand, BNYVV RNA 3 is required for vascular movement. Replication-competent RNA 3 transcripts carrying various point mutations and deletions were coinnoculated with RNAs 1 and 2 to young leaves of B. macrocarpa and the ability of the virus to multiply on the inoculated leaves and to invade the plant systemically was examined. None of the RNA 3 mutants tested interfered with virus multiplication in the inoculated leaves. Point mutations designed to specifically block or truncate translation of the ORFs of the two known RNA 3 gene products, P25 and N, did not interfere with vascular movement. Vascular movement was not inhibited by deletions eliminating the short 5'-proximal ORF on RNA 3 (ORF A) or by point mutations blocking putative translation of the short 5'-proximal ORF (ORF S) on RNA 3sub, a subgenomic RNA derived from RNA 3. On the other hand, deletions in a 'core region' encompassing nucleotides 1033-1257 of RNA 3 completely blocked vascular movement of the virus while removal of sequences flanking the core region lowered its efficiency. The observations suggest that some feature of the RNA 3 sequence rather than an RNA-3 coded protein is important for vascular movement of BNYVV in B. macrocarpa.
Lauber
E
E
Institut de Biologie Moléculaire des Plantes du CNRS et de l'Université Louis Pasteur, Strasbourg, France.
Guilley
H
H
Tamada
T
T
Richards
K E
KE
Jonard
G
G
D019663:Chenopodiaceae / Q000502:physiology / Q000821:virology*; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D018515:Plant Leaves; D010942:Plant Viruses / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012328:RNA Viruses / Q000502:physiology*; D012367:RNA, Viral / Q000096:biosynthesis / Q000502:physiology*; D017384:Sequence Deletion; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000096:biosynthesis; D014779:Virus Replication
D012367:RNA, Viral; D014764:Viral Proteins